More and more motor vehicles have, for safety purposes, monitoring systems comprising sensors mounted on each of the wheels of the vehicle, dedicated to measuring parameters, such as pressure or temperature, of the tires with which these wheels are equipped, and intended to inform the driver of any abnormal variation of the measured parameter.
These monitoring systems are conventionally provided, on the one hand, with electronic modules mounted on each of the wheels of the vehicle and incorporating, in addition to the abovementioned sensors, a microprocessor and a radiofrequency emitter, and on the other hand, with a central unit for receiving the signals emitted by the emitters, comprising a computer incorporating a radiofrequency receiver connected to an antenna.
One of the problems that such monitoring systems have to address lies in the requirement to have to associate with each signal received by the receiver of the central unit, an indication concerning the location of the electronic module and therefore of the wheel originating this signal, this requirement remaining throughout the life of the vehicle, that is to say, having to be complied with even after wheel changes or more simply reversals of the positions of these wheels. Currently, one conventional method of locating wheels on a vehicle with two axles and four wheels consists in using three low-frequency antennas each positioned close to one of the wheels of the vehicle, and in performing a locating procedure consisting in successively exciting each of these three antennas by the emission of a low-frequency magnetic field.
According to this procedure, the electronic module mounted on the wheel situated close to the excited antenna controls, in response to and addressed to the central unit, the emission of an identification signal comprising an identification code of said electronic module, such that the successive excitation of the three antennas leads to the location of the three electronic modules mounted on the wheels adjacent to these antennas, and, by deduction, to the location of the fourth electronic module.
The main benefit of such a method lies in the fact that the locating procedure is very fast and leads to almost instantaneous location after the vehicle has been started.
However, this locating method does not make it possible to discriminate the twinned wheels of vehicles equipped with axles with four wheels.
Thus, the document US 2004/0189457 implements a procedure for acquiring wheel identifying codes by placing five receiving antennas close to wheels or twinned wheel trains. However, with such antennas placed in front of a twinned wheel train (and not in front of each of the wheels) it is not possible to physically locate each of the twinned wheels, because each twinned wheel train is received by one and the same receiver which cannot discriminate the position of each of them, even if it does detect two different identifiers. Furthermore, this document requires the use of a plurality of receiving antennas, which is too costly.
Also known from the document DE 10 2006 026 527 is how to automatically acquire the identifiers of each of the wheels with which a truck trailer is equipped. However, in this document, the issue is not to locate each of the wheels, and even less to locate each of the wheels of a twinned wheel train.
Document EP 1 614 550 describes a system automatically locating the wheels of a vehicle (including twinned wheels), but this locating is performed using a separate tool (60) in which the positions of the different wheels and their identifiers are previously stored.
The present invention aims to overcome this drawback and its main objective is to provide a locating method making it possible, for a cost equivalent to the cost of implementing a method of locating wheels on axles with two wheels, to locate each of the wheels of pairs of twinned wheels with which axles with four wheels are equipped.